JPS6026981B2 - How to measure the static stability of an internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a method for determining the degree of instability (characteristic instability) of an internal combustion engine, for example in order to control the operation of the engine at the lean operating limit.

In order to cope with the currently very strict exhaust gas regulations and the usual fuel shortages, and to generally drive the car economically, the internal combustion engine is operated in an operating range that keeps harmful exhaust gas components as low as possible and fuel consumption low. Great efforts are being made to make this possible.

In order to be able to operate the internal combustion engine in this way, it is operated with as lean a fuel-air mixture as possible.

That is, the internal combustion engine is adjusted to be as "lean" as possible. This is because in this case the harmful components of the exhaust gas and the fuel consumption can be reduced in the range of lean mixtures, so that an increase in nitrogen oxides may have to be accepted to a certain degree. It is therefore of great importance to determine as precisely as possible the operating point of the lean operating limit of an internal combustion engine, for example on the basis of the fluctuations of the pressure change in the cylinder of the respective internal combustion engine. It is also known that the degree of quietness of an internal combustion engine generally decreases as the engine moves away from the stoichiometric ratio (excess air ratio: 1). The present invention is based on the recognition that the degree of non-quietness of an internal combustion engine can be measured by the fluctuation in the rotational speed of the crankshaft, since fluctuations in the pressure inside the cylinders appear as fluctuations in the rotational speed of the crankshaft due to the torque generated in each cylinder. Based on. First, in order to make it easier to understand, a detailed explanation will be given below using mathematical formulas.

However, M = engine torque T=period 0 = engine moment of inertia = rotation speed J = angle of one rotation, 360o In general, the formula M・T=8・△en holds true.

In that case sail = person = dry △ = ◇ Rawness = hair △T: T vs. 2 Therefore, the following formula is obtained.

△M●T Ni8, △ (△) Here, by substituting the value of △, the following expression is bound.

△M-T=o-person△(△T) eventually, △M～△kaiT), That is, the torque fluctuation is proportional to the three noses 2.

Therefore, the quantity related to the non-quietness of the internal combustion engine is △(△T)
, and its value can be determined from three temporally consecutive crank rotation cycles using the following equation.

l△(△T)l=l(T'xT...)-(TM-T, 12
)l As shown in the right-hand term of the above equation, the “non-quiescent degree-value” △(△T) is defined as the period T of three consecutive crank rotations.
It can be found from

The problem on which the invention is based is to provide a method for measuring the non-quiescent power value Δ(ΔT) of an internal combustion engine with as little circuit outlay as possible. According to the present invention, this problem is solved as follows.

In other words, in the method described in Masato, in order to measure the fluctuation in the rotational speed of the internal combustion engine while the crankshaft makes three revolutions, the number of rotations is calculated at a predetermined counting frequency for each cycle derived from the crankshaft rotation. 1 forward counting is performed, at the same time a second backward counting is performed at a counting frequency twice the predetermined counting frequency, and apart from these, a third forward counting is performed at the predetermined counting frequency. , and the counting state obtained in each case is transferred as the initial counting state at the start of each new period, in which case the first forward counting process starts from counting state 0 and doubles the predetermined counting frequency. A second backward counting process carried out at the counting frequency starts from the final counting state of the first forward counting process, and a third forward counting process starts from the final counting state of said backward counting process. be.
Further, according to the embodiment of the present invention, when measuring the rotational speed fluctuation of the internal combustion engine in three consecutive crankshaft rotations, the predetermined counting frequency is set to the first up-counter and the third up-counter for each cycle.
A counting frequency twice as high as the counting frequency is supplied to a second down counter, and each time the internal combustion engine rotates, the counted value is transferred to the subsequent counter, and at that time, Let the first up counter take up the contents.

The output of the third counter, which is configured as an up-counter, provides a direct output value Δ(ΔT) as a quantity representing the degree of non-quietness of the internal combustion engine for each revolution of the crankshaft or for each period. It is very advantageous to do so.

In addition, in this case, if the required counter capacity is not determined by the absolute value, but the size of the counter capacity is made to match only the maximum value of △(△T) - value, on the other hand, a very high frequency causes a sharp decomposition This is very advantageous because it allows us to obtain the desired values and, on the other hand, to reduce the cost of the circuit, as will be explained in more detail below. Also, in embodiments of the invention, the non-quiescent power values determined as described above can be used to digitally control the lean operating limits of the internal combustion engine.

The invention will now be explained in detail with reference to the illustrated embodiments.

FIG. 1 shows a digital evaluation circuit for forming, for example, a signed difference, ie Δ(ΔT), from successive rotational speed cycles when measuring the degree of non-quietness of an internal combustion engine.

By removing the parentheses from the above equation for the non-quieting degree value △(△T), we obtain the following equation: △(△T)=Ti−
2Ti 10, 10Ti+2' In that case, as mentioned above, Ti, T
i+, and Ti+2 are the periods of three consecutive crankshaft rotations. Therefore, when determining the value of △(△T) in this way, this can be carried out by three separately constructed counters 1, 2, 3, in which case when the rotation of the respective crankshaft is completed, The counting state of the final stage counter 3 directly indicates the desired non-quiet degree counting result. In this case, the first counter 1, which is configured as an up-counter, is individually supplied with a relatively high counting frequency in the range between 1 and 2 MHz.

The same frequency f is also supplied as a counting frequency to the final stage counter 3 configured as an up counter. The double counting frequency, ie 2, is fed to an intermediate counter 2 configured as a down counter.

The two required counting frequencies f and f2 can be obtained by dividing a predetermined system clock having a frequency of by a conventional frequency divider circuit 4 in a ratio of 2:1. The output of this frequency divider circuit 4 is then connected to the counting inputs of counters 1 and 3. 3 counters 1, 2
and 3, counter 2 receives the count value of counter 1 at a preset possible time, and similarly, counter 3 also receives the count value of counter 2.
It is connected to receive the count value of .

In other words, at the end of each rotation, the contents of up counter 1 are transferred to down counter 2 in parallel as the count output.
Similarly, the contents of the down counter 2 are supplied to the up counter 3 in parallel as a count value output. Only the counter 1, which is designed as a first up-counter, therefore starts counting again from zero at each crankshaft rotation. The counting start point and the count value transfer point are signals synchronized with the rotation of the crankshaft,
For example, it is controlled by a top dead center signal, ie, an OT signal.

For example, this signal can be detected by a marker 5 provided on the flywheel 6 of the crankshaft.

The marker 5 then activates the pulse shaping device 7 in each case by means of electromagnetic induction in such a way that it combines a signal for each revolution of the crankshaft. By using such a circuit, only the intermediate down counter operates at twice the counting frequency and performs count value transfer control, so that the output signal value of the final stage counter 3 accurately changes to the non-quiet degree value △(△ It can be seen that it corresponds to the term on the right of the last left indicating T).

Furthermore, such a circuit has proven to be very advantageous, since a counting device with individual counters can be constructed at low cost.

It is then not necessary to separately process the difference in speed or the period of three temporally consecutive crankshaft revolutions in each case and, on the other hand, in order to obtain a sufficiently accurate and high resolution, it is necessary to This is because it can be made very large. Furthermore, if the individual counters 1, 2, and 3 are configured so that they can completely memorize and indicate the values counted during one revolution of the crankshaft even at very small rotational speeds, very large counts of 16 bits or more can be generated. Capacity should be required. On the other hand, even at a very high counting frequency, if only the difference between the counted values is processed instead of the absolute value of the counted values, the counting capacity can be reduced based on the formation of the difference. Therefore, the counting capacity of counters 1, 2, and 3 can be kept very small by 4. For example, in a decomposition bear of one mountain s, the counting capacity can be set to only 8 bits or at most 9 bits, and finally the sign of △ (△T) can be displayed. Of course, in this case the counter should be operated at a correspondingly high counting frequency, possibly even many times per revolution of the crankshaft. However, this is not a problem in normal operation as long as the counter size or counter capacity is such that it receives the maximum of the incoming Δ(ΔT)-values. Therefore, even at very high counting frequencies with 8-9 bits per counter, i.e. 27 counting stages in total, △(△T
) is determined by the MSB of the counter 3 at the final stage. In that case, the MSB is the "most significant bit", i.e. counter 3
Indicates the most significant bit. Another embodiment of an apparatus for carrying out the method according to the invention is shown in FIG.

That is, if we examine the down counter 2 in detail in the first embodiment of the present invention, we can see that the minimum counting stage of the down counter, that is, the counting stage whose counting frequency is directly controlled by the double counting frequency, is basically the counting stage of the counter 1. It only indicates the value after a predetermined time has elapsed from the beginning based on receiving the numbers in parallel. Also, therefore, the frequency of the above-mentioned minimum counting stage is . By directly controlling the next minimum stage with the counting frequency f, corresponding to the embodiment of FIG. 2, the frequency divider 4 required in FIG. 1 is omitted. be able to. The smallest counting stage of the down-counter, designated as down-counter 2' in the embodiment of FIG. 2, need only have the function of a flip-flop memory. It is therefore also very advantageous to be able to operate the device of FIG. 2 at only one frequency f, since the resolution can be increased considerably by correspondingly increasing f. Generally used in digital technology, the sign of the processing result Δ(ΔT) is determined by the MSB value. FIG. 3 shows a control system using the circuit of FIG. 1 or 2, in which case the control device measures the lean operating limit value of the internal combustion engine using the non-quiet measurement value. and is configured to control the internal combustion engine by comparing it with a relative set value.

When controlling the internal combustion engine, the device for directly supplying the internal combustion engine with fuel is controlled in each operating state of the internal combustion engine in order to maintain it at a desired non-quiescent power value. That is, the circuit of FIG. 3 is configured to provide lean operating limit control, in which case it generates an adjustment signal that activates any fuel supply system. Also, as mentioned above, the circuits of FIGS. 1 and 2 are configured to combine the absolute value of the degree of non-quietness of the internal combustion engine.

The measured absolute value Δ(ΔT) of the non-quiet phase is then compared with a set value for control purposes, and a signal is generated when the set value is exceeded. It is also immediately obvious that this set value cannot be constant; ie, the degree of non-quietness naturally differs for different rotational speeds, so the set value should be varied accordingly. Since at very low speeds (or large periods) the actuation pulses of the crankshaft occur at large time intervals, this makes it possible to use large setpoints for low speeds.
In other words, there should be a large "acceptable" non-quiet degree value.

FIG. 4 shows a setting value that varies depending on the period, in which case the setting value changes by 1/n3 as a function of the rotational speed n.

In the embodiment of the present invention shown in FIG.
It is advantageous that a comparison of the actual values can be carried out in a simple manner, and at the same time the set value can be expressed as a function of the actual desired value as a function of the rotational speed.

For this purpose, for example, the first upcounter 1 shown in the circuit of FIG. 1 or 2 is enlarged by a predetermined number of bits by adding an additional counter la. For example, the counter 1 with the additional counter la is enlarged so that it can count the longest period of n=100 hin-1. Counter 1
and la are counted continuously and in each counting stage i
Since it is possible to take different partial frequencies (i = number of counting positions), by selecting the partial frequencies that occur accordingly, one or possibly several frequencies can be selected approximately and depending on the rotational speed. be selected. In this case, for example, this frequency can be counted in the aforementioned setpoint counter in order to form a rotational speed-dependent setpoint in a predetermined time unit. However, the frequency determined depending on the rotational speed (the fifth section that outlines the method for determining the frequency dependent on the rotational speed)
It is advantageous if the processing result counter 7' is used immediately for the counting of the processing result counter 7'. Thereby, the result counter is counted down intermittently at different frequencies. Therefore, the processing result counter 7 performs a comparison between the set value and the actual value.
' is connected to the last stage up counter 3,
In each case, the counter 3 is controlled, for example, by an OT-signal.
The setpoint-actual value comparison is carried out by receiving the contents of , retaining the contents for the period of the cycle and counting at a frequency dependent on the rotational speed.

Therefore, with the same counter, the set value is determined on the one hand, and the actual value-set value is compared on the other hand. In that case, count down using the processing result counter. Therefore, if the processing result counter overflows the zero position, the set value will not be exceeded. If the processing result counter does not reach the zero position, the actual value exceeds the set value. This condition is MS
1 directed by B and bowled directly after each rotation
Bit-signal storage 8 is stored. Therefore, when counting the process result counter as a function of the rotational speed, the excess of the set value threshold is determined by the value of the MSB of the process result counter, which value is transferred to the signal storage 8.

In this case, the frequency with which the setpoint value is exceeded in one or the other direction is indicated, which is to be effectively controlled when supplying fuel to the internal combustion engine. It is therefore advantageous to connect the integration element downstream to the signal storage 8 or to actuate the integration adjustment element directly in the signal storage. In known fuel injection systems, it is also possible to actuate a multiplier device directly with the output signal of the integrating element for shortening or lengthening the injection pulse. Therefore, in the embodiment of FIG. 3, calculations are first carried out to determine the Δ(ΔT)-value for the non-quiet degree by means of counters 1, 2, 3, and then in subsequent periods the frequency dependent on the rotational speed. is selected and a comparison between the set value and the actual value is performed. However, the speed of the entire device, which operates synchronously with the rotational speed, is not affected thereby. As shown in FIG. 4, the counting frequency of the processing result counter 7' partially changes depending on the period T, and according to the approximation law, a curve of the set value function depending on the rotation speed is obtained as shown by the broken line. .

Next, a method of generating the frequency dependent on the rotational speed indicated by block 9 in the embodiment of FIG. 3 will be briefly explained using FIG. 5. In the embodiment shown in FIG.
X2 . . . One factor partial frequency indicated by X, 6 is generated.

When a frequency of IMHz is supplied to counter 1, X, becomes 50
The frequency of Saramachi z, X2 corresponds to the frequency of 25 dish Hz, and so on. The selected frequencies X8, X9, X,3 and X,6 in the embodiment of FIG.
0, 10a, 10b, etc., and another input side of the AND gate is a bistable multipipulator 11, 11a.
, 11b, etc.

Furthermore, the switching process of the bistable multipipulator is controlled by the outputs of the individual counting stages. It is important that the set value is generated as a function of the rotational speed. This is because, in a preferred embodiment of the invention, the setpoint value is then simulated with a frequency that is dependent on the rotational speed, ie, this frequency is to be selected as a function of the rotational speed. However, as mentioned above, since the counting end point and the new counting start point are controlled by the OT- signal of the crankshaft, the output signal generated at the output side of the counting position of the counter 1 having each additional counter la is as follows. It changes depending on the rotation speed. Hence the bistable multipipulator or flip-flop 1 1,1
It is sufficient to simply use the counting state itself as a switching signal for 1a and 11b. In addition, when connecting the inputs of the individual flip-flop stages 11, 11a, 11b to the outputs of the counting positions, it is not necessary to change this depending on the respective setting. The circuit is also constructed in such a way that the output of the flip-flop 11, 11a in each case controls the input of the following flip-flop.

[Brief explanation of drawings]

1 is a block diagram briefly illustrating an embodiment of an apparatus for carrying out the method according to the invention; FIG. 2 is a block diagram illustrating an embodiment of an apparatus according to the invention requiring only one control counting frequency; FIG. 3 is a block diagram illustrating an embodiment of a control circuit implementing a method according to the invention for operating a predetermined internal combustion engine at the lean operating limit; FIG. a diagram showing the rotation speed or period dependence,
FIG. 5 is a block diagram of a frequency synthesis circuit for setting value simulation used in the present invention. 1, la, 2, 2', 3... Counter, 4...
- Frequency division circuit omitted, 5... Marker, 6... Flywheel, 7... Pulse shaping device, 7'... Processing result counter, 8... Signal storage device. Fig. l Fig. 2 Fig. 3 Fi9・muFig. 5

Claims (1)

[Claims] 1. A method for measuring non-quietness of an internal combustion engine, comprising:
In order to measure the rotation speed fluctuation of the internal combustion engine during three consecutive rotations of the crankshaft, a first forward count is performed at a predetermined counting frequency for each cycle derived from the crankshaft rotation, and at the same time A second backward count is performed at a counting frequency twice the predetermined counting frequency, and apart from these, a third forward count is performed at the predetermined counting frequency, and the counting state reached each time is converted into a new count state. transferred as a dead-end counting state at the beginning of each period, in which case the first forward counting step starts from counting state 0, and the second backward counting step is carried out at a counting frequency twice the predetermined counting frequency. starts from the final counting state of the first forward counting process, and starts the third forward counting process from the final counting state of the backward counting process. How to measure. 2. In order to measure the rotation speed fluctuation of the internal combustion engine by three consecutive crank rotations, a predetermined counting frequency is supplied to the first up counter and the third up counter each time in each period, and the counting frequency is A double counting frequency is supplied to the second down counter, and each time the internal combustion engine rotates, the counted value is transferred to the subsequent counter.
2. A method for measuring non-quietness of an internal combustion engine according to claim 1, wherein the up counter is set to zero. 3. In order to operate the second down counter at twice the counting frequency, the normal frequency f_1 is supplied to the counting stage next to the smallest counting stage of the down counter. How to measure the non-quietness of an internal combustion engine. 4. In order to compare the set value and the actual value, the count value of the final stage up counter indicating the degree of non-quietness is transferred to the processing result counter, and the processing result counter is counted during one revolution of the crankshaft. Operating limits for lean mixtures, in each case counting at a speed-dependent frequency, in which case the speed-dependent frequency is obtained by receiving the enlarged partial frequency of the first up-counter. A method for measuring non-quietness of an internal combustion engine according to any one of claims 1 to 3.